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Scroll through Instagram, and you’ll probably see enough geysers, waterfalls and northern lights to know that everyone’s going to Iceland. International visitors there have quadrupled since 2010, with nearly 2 million arriving in 2016, inundating the island nation’s 350,000 residents. So how can conscientious travelers enjoy this trending destination without overwhelming it?

Icelandic writer Alda Sigmundsdóttir, author of eight books about her home country, offers some ideas in her latest title, The Little Book of Tourists in Iceland. She’s quick to point out that the influx has been a boon to Iceland’s economy, which was devastated in the 2008 financial downturn, but accommodating so many visitors creates significant disruption to Iceland’s way of life and stretches the limits of its infrastructure. By taking some time to learn a bit about Iceland’s culture and environment, thoughtful visitors can ease the burden.

“Very often the things that locals find intolerable are things that visitors are simply not aware of, and would refrain from doing if they knew how upsetting they were to the local people,” Sigmundsdóttir says.

Here’s what to keep in mind:

To fit in, strip down.

There’s no better way to infuriate an Icelander than to flout the ironclad rules of hygiene at the country’s many thermal pools. Before you can dip so much as a toe into one of these geothermally heated pools, you must wash—with soap, buck naked—in locker-room style showers. Washing with your swimsuit on will not do.

“We are conditioned from a very young age to keep to a certain standard of hygiene at the pool,” Sigmundsdóttir says. “Those pools use very little chlorine, and the fact that there are many people sharing those pools who are not of the same mind, and do not respect that rule, puts many Icelanders off.”

Cheap airfare deals have led more people to book spur-of-the-moment trips to Iceland, which means some visitors haven’t taken the time to familiarize themselves with the country’s dangers. Sigmundsdóttir warns of avoidable injuries, even fatalities, from scalding hot springs, rogue waves that snatch tourists off the beach and winds that blow cars off the highway.

That’s not just a problem for tourists. When visitors find themselves in trouble, the people who come to their rescue are volunteers—regular folks with day jobs. They’ll drop what they’re doing and risk their lives to save strangers, Sigmundsdóttir explains, but they’d rather not have to do it for something completely preventable. So when you see a sign advising you not to do something, for heaven’s sake, don’t do it.

While top tourist draws like Gullfoss and Þhingvellir have bathrooms, many attractions in Iceland’s countryside don’t. That leads visitors to answer nature’s call in the wild, but many don’t take the extra step of burying their leavings, Sigmundsdøttir says. That’s a problem in a country as windy as Iceland: No matter how discreet a place you’ve chosen to go, the wind will relocate your used toilet paper, often to a trail, parking lot or picnic area. If you must go al fresco, bury your TP or stuff it into a rock crevice.

Camping isn’t a free-for-all.

One of the more shocking chapters in The Little Book of Tourists in Iceland details the questionable places some tourists have seen fit to pitch tents, including a bustling city street, the lawn of an historic home and an unwitting family’s backyard.

Camper vans are another offender. Because you can sleep and cook in them, they’re a popular option in a country where high-season lodging is scarce and priced accordingly, and the cheapest restaurant meals cost $20. But Icelanders feel understandably annoyed when they see public places turning into illegal campgrounds.

“This is really infuriating,” Sigmundsdóttir says, “especially because in most cases there are no toilet facilities nearby… and we all know what that means.” (see #3.) The solution: Stick to designated campgrounds.

Watch your language.

No one expects tourists to converse in Icelandic, a notoriously difficult language. But as tourism brings in English-speaking workers from other countries, Icelanders sometimes have to conduct their daily tasks in English because the workers don’t speak Icelandic. While preserving the Icelandic language is beyond the reach of tourists, it wouldn’t hurt for visitors to show respect for the culture by learning a few words, Sigmundsdóttir says. And don’t assume everyone speaks English.

“It always rubs me the wrong way when people walk up to me on a street in a country where the native language is not English, and start speaking to me English,” she says. “Even though most people in Iceland DO speak English, I think it shows courtesy at least to ask ‘Do you speak English?’ before launching into a question.”

Stick to the road.

Iceland’s wide-open expanses might give you the urge to go off-road in your rented 4x4 vehicle, but you’d be destroying sensitive landscapes that could take decades to recover. Driving off-road is illegal and carries hefty penalties: Just ask the drivers slapped with $13,000 in fines in August after they carved up two natural areas with their 4x4s.

Be a good neighbor.

For residents of downtown Reykjavik, the sound of suitcase wheels clattering over the pavement beneath their bedroom windows isn’t exactly a lullaby. Keep sleeping neighbors in mind when checking in and out of your lodging in the wee hours and when returning from Reykjavik’s legendary nightlife.

Something else to consider: As in many cities, the rise of short-term rentals like Airbnb has proved a mixed blessing for Reykjavik, Sigmundsdóttir says. Rentals help ease the lodging shortage and provide extra income for residents, but investors who buy properties exclusively for vacation rentals deplete the housing stock in an already expensive city. For this reason, Sigmundsdóttir suggests renting from someone who actually lives in the home.

Book with certified companies.

Hotels, guides, and tour operators have sprung up to satisfy the demands of the tourism boom, but not all follow sustainable practices. To ensure your service providers are above-board, you can book companies certified by Vakinn, a program run by the Icelandic Tourist Board.

There’s a self-serving reason to go with Vakinn-accredited vendors, as well.

“Those companies have to adhere to a certain standard when it comes to quality, and not least safety,” Sigmundsdóttir says. “Iceland is a country in which keeping to safety standards can sometimes mean the difference between life and death.”

For more of Sigmundsdóttir insights into how visitors can make sure their visit to the country is sustainable, check out her book.